[gmx-users] energy minimisation of carbon nanotubes.
elie.moujaes at hotmail.co.uk
Sat Sep 15 18:49:15 CEST 2012
I have a small question regarding energy minimization. I am minimizing a carbon naotube in vaccuo and my (mdp )input file is: ;
; SWNT (10,0) on its own
; Elie Moujaes, SWNT+polymers project
; Energy minimization input file
; Energy minimizing stuff
emtol = 0.00001
pbc = xyz
periodic_molecules = yes
rlist = 1
rcoulomb = 1.0
rvdw = 1.0
I have put emstep very loww toa chieve accuracy.In the output i got:
Reading file SWNT-EM.tpr, VERSION 4.0.5 (single precision)Polak-Ribiere Conjugate Gradients: Tolerance (Fmax) = 1.00000e-05 Number of steps = 2000 F-max = 3.48055e+03 on atom 799 F-Norm = 9.67779e+02
Stepsize too small, or no change in energy.Converged to machine precision,but not to the requested precision Fmax < 1e-05
Double precision normally gives you higher accuracy.
writing lowest energy coordinates.
Polak-Ribiere Conjugate Gradients converged to machine precision in 359 steps,but did not reach the requested Fmax < 1e-05.Potential Energy = 8.7646348e+03Maximum force = 1.6186214e+01 on atom 701Norm of force = 5.4860659e+00
It seems that I have to use the double precision version but as the single precision is concerned,Is the minimization fine (as the maximum force on atom 701 is 16...)?
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